To find the Android version go to About Phone in Settings at the bottom.Android 10 (which lacks a confectionery themed code name) is the most recent version, and while it and its predecessors Android 9 (Pie) and 8 (Oreo) are still in getting security updates, using anything below Android 8 "will carry security risks," Which? said.
Based on Google's own data from last year, around 40% of Android active users worldwide are on version 6.0 or earlier: Marshmallow (2015), Lollipop (2014), KitKat (2013), Jellybean (2012), Ice Cream Sandwich (2011) and Gingerbread (2010). According to the Android Security Bulletin, there were no security patches issued for the Android system in 2019 that targeted Android versions below 7.0 (Nougat).
Then look for Software Information.